The present invention relates to a method and apparatus for making a blow-molded plastic container and a corresponding closure, and more particularly, the present invention relates to an efficient method and apparatus for the simultaneous manufacture of blow-molded containers and compression-molded closures within blow molds.
Various consumer products, such as beverage, food and other products, are packaged for sale in blow-molded plastic containers sealed with a plastic closure. Typically, the containers are mass produced in high speed rotary blow-molding machines, and the closures, such as caps and lids, are manufactured separately from the containers in injection molds. The separate manufacture of the containers and closures has a significant impact on the overall cost of mass producing the packages. These costs include manufacturing, tooling and material costs.
Another disadvantage of manufacturing containers and closures utilizing different molding processes is that such processes require the use of different plastic materials which results in the containers being made of one type of plastic material and the closures being made of another. Such a package complicates and increases the cost of recycling the containers and closures and does not readily permit precise color matching between the containers and closures. Thus, the separate manufacture of the containers and closures also has a negative impact on the aesthetic appearance of the package and its ability to be recycled in a cost-effective manner.
The above referenced problems are addressed in U.S. Pat. No. 6,290,094 which is assigned to Graham Packaging Company, L. P., the assignee of the present application. The patent discloses a method of compression molding a closure in the flash material formed in an extrusion blow mold during the manufacture of a blow molded container. To this end, a tubular parison of molten thermoplastic material is extruded within a blow mold which has a container body cavity and an adjacent lid cavity. A lower section of the parison is received and blown in the container body cavity to form a blow-molded container body, and an upper adjacent section of the same parison is received and compressed in the lid cavity to form a compression molded lid for the blow molded container. A live hinge is formed between the lid and container so that the lid is tethered to the container and pivotable relative to the container between open and closed positions. Thus, the lid is formed in the blow mold from material which would otherwise form flash and be severed from the container and recycled as scrap material. This method provides a package which is of a consistent color throughout and which can be efficiently recycled in its entirety.
Graham Packaging Company, L.P. is also the assignee of co-pending U.S. patent application Ser. No. 09/618,170 which was filed on Jul. 18, 2000 and which discloses another method of forming a container and lid combination within a blow mold. The lid is formed utilizing a combination of blow-molding and compression molding techniques to provide a lid having a reinforced blow-molded central section and an outer peripheral compression-molded section. This method and lid structure permits the formation of closures which are manufactured in the so-called flash material within a blow mold and which are particularly useful in connection with wide mouth container bodies, such as tubs and the like.
Other examples of forming articles in the flash material compressed in blow molds include U.S. Pat. Nos.: 4,082,827 issued to Chlystun; 5,165,558 issued to Cargile; 3,359,602 issued to Bailey; 3,369,690 issued to Hayes; 3,679,785 issued to Dike; 5,275,780 to Robinson; and 3,983,199 issued to Uhlig. The Chlystun patent discloses compression molding an integral pull tab; the Cargile patent discloses compression molding a breakaway measuring cup; and the Bailey, Hayes, Dike, Robinson and Uhlig patents disclose compression molding an integral handle.
In addition, other U.S. patents disclose the formation of blown closures within the container body cavity of a blow mold. To this end, the container body and closure are blown as a single intermediate body within a blow mold cavity. The blown intermediate article is then severed and trimmed to form a separate container body and closure. See for instance, U.S. Pat. Nos. 5,553,732 and 5,762,859 issued to Kani; 5,044,923 and 5,213,753 issued to Przytulla; 3,409,710 issued to Klygisis; and 5,865,338 issued to Conn.
A typical type of blow molding machine utilized to manufacture blow molded containers is a wheel blow molding machine which is vertically disposed and rotates about a horizontal axis. An example of such a machine is illustrated in FIG. 1 of U.S. Pat. No. 5,681,597 issued to Aguilar et al. and by the discussion provided in the Aguilar patent on column 2, line 52 to column 3, line 23. To this end, the blow molding machine has a plurality of molds positioned in a circular array following a circular path of motion. Each mold has a pair of mold halves which open to receive an extruded hollow parison, which close thereon so that the parison can be blown into conformance with the cavity defined by the mold, and which thereafter, open to release the blown article. All of these operations occur as the wheel continuously rotates at a constant speed, thereby forming and releasing blown articles in a continuous manner.
In an effort to increase the rate of manufacturing blown articles in a blow-molding machine, U.S. Pat. No. 3,432,586 issued to Stenger and 3,862,698 issued to Hafele disclose forming in each blow mold a pair of blown container bodies which are integrally connected by ring-shaped flash material. The flash material ring is severed from the containers to separate the containers into two identical separate container bodies. This concept can be utilized to effectively double the output of bottles that can be formed during each revolution of a wheel blow molding machine.
Further, it is also known to simultaneously extrude multiple separate parisons within a blow mold to simultaneously form multiple separate blown articles in each mold. For instance, see co-pending U.S. patent application Ser. No. 09/877,892 which was filed on Jun. 8, 2001 and which is assigned to Graham Packaging Corporation, L. P., and see U.S. Pat. No. 5,551,862 issued to Allred, Jr., 4,861,542 issued to Oles et al., and 3,802,823 issued to Doughty et al. The above referenced application discloses a blow mold capable of receiving a pair of simultaneously extruded parisons and capable of forming four blown bottles, two by two, within each mold. The molds are carried on a vertically disposed wheel blow molding machine having twenty-four identical such molds thereby forming 96 bottles per revolution of the wheel blow molding machine.
Although the above referenced container and closure combinations and/or the above referenced methods and apparatus for manufacturing containers and/or closures may function satisfactorily for their intended purposes, there is a need for a novel method and apparatus for the cost-effective manufacture of container and closure combinations. The container and lid combination should be capable of efficient and simultaneous manufacture in the same blow mold, should be readily recyclable, and should have substantially flawless color matching, if desired.
With the foregoing in mind, a primary object of the present invention is to provide a novel method for efficiently forming a plastic container and associated closure in the same blow mold utilizing a combination of blow molding and compression molding techniques.
Another object of the present invention is to a provide apparatus for making a plastic container and associated closure simultaneously in the same blow mold.
A further object of the present invention is to produce a complete package including a container body and closure at an increased production rate and with reduced machine capital and tooling costs.
Yet another object of the present invention is to a provide a complete package including container body and closure which have substantially perfect color matching and which are made of the same material enabling ready one step recycling of the entire package.
More specifically, the present invention provides a method of manufacturing a plastic container and closure combination in which at least one tubular parison of molten thermoplastic material is extruded into an open set of mold blocks. When closed, the mold blocks cooperate to form at least one container forming cavity spaced from at least one closure forming cavity. The set of mold blocks are closed to capture the at least one parison and a hollow container body is blow-molded within said container forming cavity while a closure is simultaneously compression-molded within the closure forming cavity. The container body has a finish and the closure is of a predetermined size for use in engaging the finish to seal the container body thereby forming an entire package.
Preferably, a first and second parison are simultaneously extruded into the open set of mold blocks, and the first parison is blow-molded in the container forming cavity and forms the blow-molded container body while a portion of the second parison is simultaneously compression molded in the closure forming cavity to form a compression-molded closure. In addition, preferably the set of mold blocks provide a pair of container forming cavities and a pair of closure forming cavities so that two blow-molded container bodies and two compression-molded closures are simultaneously formed in the set of mold blocks. In this case, the first parison is utilized to form the pair of container bodies and the second parison is utilized to form the pair of closures.
According to another aspect of the present invention, a novel apparatus for manufacturing plastic container and closure combinations is provided. The apparatus includes a set of mold blocks which, when closed, define at least a pair of separate, elongate, laterally spaced-apart, parison-receiving cavities. One of the parison-receiving cavities has at least one container body forming section and the other of the parison-receiving cavities has at least one closure forming section. The set of mold blocks are capable of simultaneously receiving and clamping on a pair of spaced-apart, simultaneously-extruded parisons such that at least a portion of one of the parisons is receivable in the container forming section for forming a blow-molded container body and at least a portion of the other of the parisons is simultaneously receivable in the closure forming section for simultaneously forming a compression molded closure in the set of mold blocks. Preferably, one of the parison-receiving cavities has a pair of container body forming sections and the other of the parison-receiving cavities has a pair of closure forming sections for simultaneously forming two separate container bodies and two separate closures.